ED Decision 2009/005/R
Each mixed balloon using disposable ballast must have means for safe storage and release of the disposable ballast. (See AMC 31HB.51)
ED Decision 2009/005/R
Ballast material should be easily transferred, disposed of and dissipated. Means should be provided to prevent freezing and/or blocking the release of the ballast material. The material should not pollute the environment.
Dry sand is a well proven material and is considered as suitable in the sense of this paragraph and this AMC.
The disposable ballast may be necessary for the pilot to perform the flight path management. The pre- take-off decision on the amount of disposable ballast should be left to the pilot as it is dependent on the flight task, the weather etc.